The purpose of this project is to investigate the genetics, immunology and pathology of retroviral infections. Specifically, we use mice infected with Murine Leukemia Viruses as models to study retroviral neurovirulence, immunological resistance mechanisms, and vaccine protection. The project involves the use of genetically identical mice to study specific effects from viruses containing defined genetic differences. We also use genetically distinct mouse strains (congenic, transgenic and knockout strains) to identify resistance genes, and to relate genetic resistance to specific immunological mechanisms. In addition, we also use these mice to test vaccines and immunological responses. The basic knowledge gained from these studies is relevant to human diseases such as HIV-associated dementia, HTLV I-induced leukemia, and AIDS.